CVE-2015-0685 in IOS XE
Summary
by MITRE
Cisco IOS XE before 3.7.5S does not properly handle route adjacencies, which allows remote attackers to cause a denial of service (device hang) via crafted IP packets, aka Bug ID CSCub31873.
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Analysis
by VulDB Data Team • 05/02/2022
Cisco IOS XE software versions prior to 3.7.5S contain a critical vulnerability in the routing protocol implementation that enables remote attackers to trigger device hang conditions through carefully crafted IP packets. This vulnerability specifically affects the handling of route adjacencies within the routing table management system, where the software fails to properly validate or process certain packet structures that influence routing decisions. The flaw exists in the underlying network protocol stack where route adjacency information is processed and maintained, creating a condition where malformed or specially constructed IP packets can cause the device to enter an unstable state.
The technical implementation of this vulnerability stems from insufficient input validation within the routing adjacency processing code. When the affected IOS XE devices receive crafted IP packets containing malformed routing information or unusual adjacency parameters, the routing protocol engine attempts to process these inputs without adequate safeguards. This leads to memory corruption or state machine inconsistencies that ultimately result in device hang conditions where the routing process becomes unresponsive. The vulnerability operates at the network layer and affects the core routing functionality of the device, making it particularly dangerous as it can impact network availability and connectivity.
The operational impact of CVE-2015-0685 extends beyond simple denial of service as it can cause complete device unavailability, requiring manual intervention or device reboot to restore normal operations. Network administrators may experience extended downtime as the affected devices become unresponsive to management traffic while still processing incoming packets. The vulnerability affects routers and switches running Cisco IOS XE software, particularly those configured with dynamic routing protocols such as ospf, bgp, or eigrp, where route adjacencies are actively maintained. This creates a significant risk for enterprise networks, service providers, and critical infrastructure where continuous network availability is paramount.
This vulnerability maps to CWE-129 Input Validation and Output Encoding, specifically addressing improper validation of input data within network protocol processing. From an attack perspective, this aligns with techniques described in the MITRE ATT&CK framework under T1499 Network Denial of Service, where adversaries exploit weaknesses in network infrastructure to disrupt service availability. The attack requires remote access to the network and the ability to inject specially crafted IP packets, making it a significant threat vector for network-level attacks. Organizations should implement network segmentation and access controls to limit exposure, while also applying the vendor-provided security patches to mitigate the risk of exploitation.
The recommended mitigation strategy involves immediate deployment of Cisco IOS XE software version 3.7.5S or later, which contains the necessary code fixes to properly handle route adjacency processing and validate incoming packet structures. Network administrators should also implement ingress filtering and access control lists to limit the sources of routing updates and reduce attack surface. Monitoring should be enhanced to detect unusual routing behavior or packet patterns that may indicate exploitation attempts. The vulnerability highlights the importance of robust input validation in network protocol implementations and demonstrates how seemingly minor flaws in routing code can have significant operational impacts on network infrastructure reliability and availability.